1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier and a control method therefor.
2. Description of the Related Art
Generally, image formation of an image forming apparatus such as a copier is composed of a series of processes of forming an electrostatic latent image of an image carrying member such as a photosensitive drum, adhering toner on the image carrying member by a developing device, and transferring the toner on the image carrying member onto a recording sheet. In this case, before moving to the next image forming process, it is necessary to clean the residual toner kept adhered on the image carrying member.
As indicated in Japanese Patent Publication Application No. 63-278087, in the cleaning device used in the image forming apparatus, the method for scraping off the toner on the image carrying member by a rubber blade is used predominantly. However, the rubber blade is always in contact with the image carrying member, so that if a foreign substance is held between the rubber blade and the image carrying member, defective cleaning may be caused, thus an inferior image is formed. Therefore, to prevent defective cleaning due to paper powder adhered to the blade, when the printing is finished, a method for separating the blade from the image carrying member or slightly rotating reversely the image carrying member is known.
However, to the reversely rotating amount of the image carrying member, there is a physical limit of preventing an occurrence of a mechanical distortion such as twisting or bending in a recovery blade installed in the cleaning device or of an inferior image due to a fall of toner. Due to this limit, a problem arises that particularly a foreign substance such as a mixture of paper powder and toner or powder is caught in the rubber blade edge or stays between the recovery blades, thus stains are hardly removed.